1. Field of the Invention
The present invention relates to a method for molding a small form factor memory card and, more particularly, to a shape-molding structure of memory card having an smooth and intact outer appearance.
2. Description of Related Art
Memory cards are widely utilized in various electronic products such as digital cameras, mobile phones, personal digital assistants (PDAs), and so on. The size of memory cards has decreased steadily over time. For instance, at the present time, the length and width of some memory cards (e.g., microSD cards or MMC Micro cards) is smaller than 1 cm, and their thickness is smaller than 1 mm.
U.S. Pat. No. 6,624,005, entitled “Semiconductor memory cards and method of making same,” discloses a method of making a memory card that can cut through the body and the printed circuit board sheet, or panel substrate, in a “cookie cutting” pattern, after the encapsulating molding process is carried out. The above-identified process functions most efficiently if the memory card itself is rectangular or if there are straight lines at the sides of memory card.
Typically, as the memory card has developed, it has evolved into a more complex shape, as in the case of miniSD and microSD memory cards. As a consequence of this more complex shape, the memory card poses great challenges in the manufacturing process after the encapsulating molding process has been carried out. First, the cookie cutting process as described in the above-identified patent no longer works in an efficient and satisfactory manner. Second, the chamfer that needs to be cut involves cutting not only a two-dimensional corner, but also involves the three-dimensional aspect of the height and thickness of the card, as is the case with microSD cards.
Several conventional approaches are available to address the cutting of the complex shape of the memory card. After the encapsulating molding process has been completed, as is shown in FIG. 1, the memory cards 30 on a substrate panel 52 are cut or singulated using a water-jet machine, a precision laser, or a grinder. As the shape cutting process requires three-dimensional consideration, the process is very time-consuming and not cost effective.
An improvement to address the complex shape cutting process is thus required in order to reduce the time and cost in manufacturing. To address this in a conventional approach, instead of utilizing the previously-described cookie cutting approach, a group of individual shape-molding is required to take care of the complex shape. The only parts of the memory card that need to be cut are those that have straight lines, but not those with a complex shape. A water-jet machine, a precision laser, or a grinder is no longer required to perform complex but single-task cutting onto the memory card. Instead, a standard router, singulator or punch, as can be found in a standard semiconductor back-end process, is sufficient to detach or remove the finished molded memory card from the panel substrate.
As shown in FIG. 1A, a conventional memory card structure includes a circuit substrate 10 having an upper surface and a lower surface. A circuit layer 12 and a plurality of electric contacts 14 are located on the upper surface and the lower surface of the circuit substrate 10, respectively. A memory chip 16, a control chip 18 and several electronic components 20 are located on the upper surface of the circuit substrate 10 and electrically connected with the circuit layer 12. An encapsulant covering 22 encapsulates the circuit substrate 10 and all the above components on the upper surface of the circuit substrate 10 with only the electric contacts 14 on the lower surface of the circuit substrate 10 exposed for electric connection with the outside.
The method of forming the encapsulant covering 22 conventionally utilized in the prior art is described below. First, the circuit substrate 10 is placed on a lower mold surface of a mold 24. The mold 24 has an encapsulant inlet 26 located above the circuit substrate 10. Encapsulant will be injected in the encapsulant inlet 26 above the circuit substrate 10 to encapsulate the circuit substrate 10, the memory chip 16, the control chip 18 and the electronic components 20. After the encapsulant hardens, the memory card is taken out from the mold. FIG. 1B shows a conventional molding process in progress with encapsulant inlet on top of the memory card 30 mold. FIG. 1C shows a finished product memory card 30. However, a trace mark 28 of the encapsulant inlet will remain on the surface of the finished product of memory card 30. Because the memory card 30 structure is so small, once there is any appearance flaw (e.g., the trace mark 28 of the encapsulant inlet 26 in FIG. 1C) remaining on the outer surface of the memory card 30 during the manufacturing process, this appearance flaw will be very obvious. Moreover, the size of future memory cards will tend to be even smaller, making any appearance flaw located on memory cards even more difficult to ignore.
Accordingly, the method and system in accordance with the present invention provides a molded structure of the memory card in order to solve the above drawback in the prior art.